A waveguide system provides a medium through which electromagnetic waves are transmitted. For instance, an optical waveguide system transmits optical waves. The two most common types of optical waveguides are rib-form waveguides and buried-channel waveguides.
A rib-form optical waveguide system is typically formed by providing multiple core channels, each of which transmit optical signals, on top of a cladding layer that has a relatively lower index of refraction, IOR. Above the cladding layer, the core is exposed to ambient air that forms an “air cladding.” Air also has a lower index of refraction compared to that of the core (IORair approximately equals 1). Parallel arrangement of these exposed channels lend to the name “rib-form” waveguides. Light can be guided through the core since the index of refraction of the core is relatively higher than that of the surrounding claddings. The very low index of refraction of the air cladding allows the waveguide system to effectively guide light through bends or curves without excessive lost of light. One disadvantage, however, is that the air cladding can leave the core channels exposed to physical damage and contamination from dust and other types of contaminants.
When waveguide systems include an additional cladding layer to sandwich the core channels between the two cladding layers, the waveguide system is commonly referred to as a buried-channel waveguide system. The buried channel waveguide system is more structurally sound since the channels are completely covered (or “buried”) and thereby protected by the additional cladding layer. Unfortunately, the index of refraction of the additional cladding layer is typically higher than that of air. This means that buried-channel waveguide systems are less able to guide light through curves without losing a large amount of light through each turn. To avoid excessive loss of light, the core channels must be formed such that the turns have larger turn radii. Unfortunately, this causes waveguide systems to occupy a larger footprint in systems that typically put a premium on maintaining small form factors.
In light of the constant miniaturization of computing systems and the increased use of optical transmission systems, waveguide systems that have smaller form factors and that are able to endure physical handling during manufacturing processes would be desirable.